Engaging men and boys to prevent violence against women and improve health outcomes for both sexes is recognized by major global health organizations as a critical public health strategy. A growing body of research has found that males' inequitable attitudes and behaviors (gender inequitable practice) are associated with poor health outcomes for males and females. This research Infrastructure development project focuses on understanding mechanisms for the emergence of gender inequitable practice in early adolescence and how to change cultural norms around masculinity. The project Is significant because 1) this Is the first study to examine the developmental trajectory of gender inequitable practice from middle to high school years to highlight critical junctures for intervention; 2) culturally relevant, age-appropriate measures for gender attitudes and behaviors are needed to evaluate the effectiveness of gender-specific prevention efforts; and 3) none of the research-tested violence prevention programs among adolescents to date have demonstrated significant changes In gender attitudes, pointing to the need for this study on whether and how gender inequitable practice may be modified during adolescence. Innovations are first, a trans-disciplinary approach, which combines gender theory, adolescent development, and community-partnered research to conduct an analysis of gender Inequitable practice in adolescence; second, the use of unique approaches Involving youth to inform basic behavioral research In adolescence; and third, inclusion of stakeholders In a realist-Informed review of gender-specific prevention programs. This community-partnered project builds on an existing partnership with an economically and ethnically diverse school district in Pennsylvania, and capitalizes on the planned Implementation of a gender-specific violence prevention program called Coaching Boys Into Men (CBIM). Concept Mapping and Visual Voices - participatory research methods - will be used to assess how young males and adults think and talk about masculinity (Aim 1). Community partners will participate in a 'realist-Informed' systematic review of gender-specific prevention programs to Identify strategies for changing masculinity norms (Aim 2). Finally, measures for gender-inequitable practice and associated behaviors will be revised and tested for understandability, face and construct validity with middle and high school male athletes participating In CBIM (N=150) along with in-person observations of the delivery of this program targeting adolescent males (Aim 3). This community-partnered project is expected to translate into improving the timing, approach, and measures utilized In gender violence prevention and related public health programs with the goal of changing cultural norms around masculinity.